Various systems are available for the ignition or detonation of propellant and explosive charges. In addition to the more conventional and older electrical or chemical ignition systems, signal tube transmission systems have been proposed for use in various applications. Signal tubes and their use in various applications are described in "Explosives and Rock Blasting," Atlas Powder Company, Dallas, Texas, 1987, at pages 139-151. Described in its simplest terms, such a signal tube comprises a tubular member which contains reactive material that transmits a firing signal through the tube upon initiation by any suitable means such as electrical or chemical detonating means.
Specific low brisance energy transmission devices of the type employing signal tubes are disclosed in U.S. Pat. No. 4,290,366 to Janoski. Among the transmission devices disclosed in Janoski are elongated tubular members formed of polymeric materials which contain filaments of a self-oxidizing material such as nitrocellulose. The guide tube may be formed of a material such as polyethylene, polypropylene, polyvinylchloride, polybutene, ionomers, nylons and the like, and the strands of self-oxidizing material can be in the form of a mono-filaments or multi-filaments such as woven or spun threads. Any suitable self-oxidizing material which is capable of propagating an explosive signal through the elongated plastic tube without rupturing the tube can be employed. The self-oxidizing material may be unmodified nitrocellulose or a chemically modified nitrocellulose such as a halogenated derivative. Alternative self-oxidizing materials include filaments extruded or molded from flexible plasticized explosives compositions containing RDX, HMX or the like. The strands of self-oxidizing material can also be coated with modifying material such as flaked or atomized aluminum, RDX, HMX, PETN and similar materials.
U.S. Pat. No. 4,220,087 to Posson discloses a linear ignition fuse for use in gas generators and the like. The ignition fuse of Posson comprises a core of nondetonating ignitive material comprising a mixture of particulate fuel, oxidant and binder disposed within a frangible tubular sheath formed of materials such as plastic, metal, ceramic or composite material. Various core materials are disclosed in Posson and include a plurality of strands formed of materials such as glass fibers, metals, or polymeric materials coated with an ignitive mixture of powdered fuel, oxidant and a suitable binder. Fuels disclosed in Posson include aluminum, magnesium, titanium, boron and zirconium/nickel alloy, and oxidants include alkali metal, alkaline earth metal or ammonium nitrates, polychromates or perchlorates, including specifically potassium and ammonium perchlorate.
In the Posson system, the reaction travels down the fuse at a velocity of about 1000-1500 meters/sec, and the sheath is shattered, projecting small incandescent particles radially from the fuse. Reinforcing strands formed of fiberglass or metal wire may be wrapped about the outer surface of the sheath and spaced to leave unreinforced areas in order to distribute the effect of the reaction in rupturing the sheath. The Posson system, like the Janoski system, provides for a low brisance energy transmission system. As described in Posson, a length of the fuse was taped to an unsupported 0.040" sheet of soft aluminum and ignited with no visible deformation of the aluminum sheet.